Hob for generating bevel-gears



C. G. OLSON. HOB FOR GENERATING BEVEL GEARS.

2 SHEETS-SHEET I.

Patented N 0V. 22, 1921.

APPLICATION FILED NOV. 24, I920- C. G. OLSON.

HOB FOR GENERATING BEVEL GEARS. APPLICATION HLEb NOV. 24. 1920.

. 397 97; Patented Nov. 22, 1921.

2 SHEETS-SHEET 2.

LOCATION OF Q FJDHiIiT ACTION -LJJJJJ UNITED STATES PATENT OFFICE.

CARL, e. oLsoN,or CHICAGO, ILLINOIS, ASSIGNOR T ILLINoIs TooL woRKs, ordIIIoAeo, ILLINoIs, a CORPORATION or ILLINoIs.

( I HOB FOR GENERATING BEVEL-GEARS.

Specification of Letters Patent.

Patented Nov. 22. 1921.

Application filed November 54, 1920. Serial No. 426,292.

To all whom it may concern: Be it known that I, CARL G. OLsoN, a citizenof the United States, residing at Chicago, in the county of Cook andState of Illinois, have invented a 'certain'new and useful Improvementin Hobs for Generating Bevel-Gears,-of which the following is aspecification.

My invention relates to hobs and the object is to produce a hobcapableof generating bevel gears. To facilitate an understanding of theprinciple of the invention, I will call attention to the fact that thetype of bevel gears known as skew bevel gears is often used fortransmitting motion in various types of machines. -When skew gearscooperate, there is a sliding action of one upon the other lengthwise ofthe body of the intermeshing teeth and I have discovered that this factcan be taken advantage of to produce a hob capable of generating a bevelgear.

In the accompanying drawings, I have illustrated a hob embodying myinvention, a bevel gear producible by the hob, and a machine capable ofemploying the hob to produce a bevel gear. In these drawings Figure 1 isa face or axial view of a considerable portion of a hob embodying theinvent-ion. This figure also shows in dot-anddash lines, the positionwhich the bevel gear blank and arbor will occupy during the generatingoperation.

Fig. 2 is similar to Fig. 1 except that por-. tions of the hob and ofthe bevel gear are,

. looking in the direction of the axis .of the latter, and showing inelevation the region of action of the hob upon the gear.

Fig. 5 is a perspective View of the region of action of the hob uponthegear.

Fig. 6 is an elevation of a machine adapted to employ the hob to producea bevel gear.

Like numerals denote like parts throughout the several views.

In the form selected to illustrate the invention, the bevel gearproduced is an ordinary bevel pinion-that is,', it is a; pinion in whichthe longitudinal axes of the teeth converge at a common point located onthe produced axis of the gear. The hob itself resembles in general, askew bevel gear such as would mesh and cooperate with such a bevelpinion. As usual in skew-gearing the axes of the two intermeshingelements do not lie in a common plane, but are offset from each other.In the drawings, the bevel gear is indicated by the reference letter G,and the hob in general by the reference letter H. The axis of the gearis oifset from the axis of the hob a distance equal to the radius of thedot-and-dash circle 5, Figs. 1 and 3.

As previouslystated, the hob resembles a skew bevel gear, thelongitudinal axes of the teeth, indicated by the light lines 6, Fig. 1,all running tangent to the circle of offset 5. The teeth, however,instead of being continuous from end to end, are traversed by flutes 0rgashes 8, which produce a plurality of hob teeth in longitudinalalinement. The

,gashes are not concentric with the hob, but

are eccentric, and in the illustrated case are struck on radii indicatedby the dot-anddash lines 10, shown in Fig. 1. These radii are here shownas being struck from a circle 12 which coincides with the inner diameterof the'hob. The length of the radii is shown as bemg somewhat greaterthan the radius of the circle 12. These dimensions, proportions andrelative locations may, however, be varied.

It is preferable to use a number of gashes or flutes which is prime tothe number of rows of teeth in the hob. This provides a condition whichproduces smoother work, as

a greater number of teeth comes in contact with the work and the cutsare more closely distributed over the surfaces of the work.

To facilitate cutting, the hob teeth are so formed as to affordclearance or relief back of the cutting edges as is the common practicein hobs and cutters. The clearance or relief is illustrated at ,the leftportion of Fig. 2. While the manner in which the hob is produced is,strictly speaking, immaterial in this present patent, it may be statedthat the forming of the teeth in the blank to first produce theequivalent of a skew bevel gear is preferably accomplished by firstremoving the greater portion of the stock between the teeth to beformed, with a tool preferably of the rotary cutter type, although atool of the one point type as used in a planing machine may besubstituted. To finish the hob, or practically finish it, there may beused a hob such as the one described and claimed in my copendingapplication filed November 24, 1920, Serial No. 426,293.

t In practice, the hob is used in the manner illustrated in Fig. 6. Inthe form of the machine there illustrated the hob is secured to an arbor16, journaled in the machine frame 17 and rotated by a worm wheel 18which meshes with a worm 20 fastened to a. drive shaft 21. This driveshaft is rotated by a band wheel 22 or other suitable form of powerdevice and has fastened to it a spur gear 24 which meshes with a spurgear 25 for imparting rotation to the work G. In the constructionillustrated, gear wheel 25 is fastened to a shaft 26 provided with abevel gear wheel 28, which meshes with a bevel gear wheel 29, rigidlyfastened to a vertical shaft 30. Shaft 30 has splined to it a bevel gearwheel 32 which meshes with a bevel gear wheel 33, the latter being fastened to or integral with a concentric bevel gear wheel 34 which mesheswith a bevel gear wheel 36 splined to the work spindle 3.8. The bevelgear blank or work G is fastened to said spindle and the spindle itselfis journaled in a sleeve or housing 40, mounted upon and rotatable withthe indexing head 42. Said head is mounted upon the vertically movablecarriage 44 of the machine, and is rotatable about an axis concentricwiththe axis of the gear wheels 33, 34. This makes it possible toproduce bevel gears of different degrees of bevel. The carriage isVertically movable in guides 46 carried by a horizontally movablecarriage 48 mounted upon the main frame 17 Carriage 44 may be raised andlowered by means of a handwheel 50 together with a feed screw and nut(not shown). As mechanisms for causing a carriage to travel along itsguides are well known, they need not be described in detail here.

It will be obvious by reference to Fig. 6 and the foregoing descriptionthereof, that the hob H and gear blank G rotate in synchronism abouttheir respective axes as is usual in hobbing machines. In using my hob,however, the work is fed toward the face of the hob in a directionparallel to the hob axis, and the feed causes the tool to sink from topto root of the teeth of the work.

In operation, as the hob and the blank rotate, as soon asthe two comeinto contact, a sliding action takes place, after the manner of ordinaryskew gears. This slid ing action causes the teeth of the hob to cut themetal of the gear blank and as the latter is fed downward the teeth areradually formed. The region of ,action 0 the hob upon the work isindicated by the shaded mately indicated in perspective at 54 l ig. 5. i

From the foregoing, it will be seen that my hob is capable ofgenerating, with a single setting and without any indexing orspacingoperation, a bevel gear which is accurate theoretically as well aspractically.

Having thus described my invention, what I claim as new, and desire tosecure by Letters Patent is: 1. A hob having the general configurationof a skew bevel gear, the hob teeth being separated, lengthwise, bycross flutes -or gashes. 2. A hob of the general form of a skew b'evelgear, said hob having cross flutes whereby a plurality of hob teethoccur in alinement with each other, the cross flutes being approximatelyat right angles to the longitudinal axis of the tooth.

3. A hob having the general form of a skew bevel gear, the hob havingarcuate flutes or gashes which are struck from a center remote from theaxis of the hob.

4. A hob having the general form of a skew bevel gear, the hob havingarcuate flutes which are struck from a center remote from the axis ofthe hob, the number of flutes being prime to the number of rows of hobteeth. I

5. A hob of the general form of a skew bevel gear in which each tooth ofthe bevel gear is divided into a plurality of sections interspaced bytraversing flutes, said sections being relieved for clearance after themanner of the teeth of an ordinary hob or cutter. I

6. A hob having the general form of a skew bevel gear in which the teethextend from the outer periphery of the gear to an inner circle remotefrom the axis, the hob having arcuate gashes struck-upon radii the locusof the centers whereof is a circle of a diameter not less than theoffset circle 5.

7". A hob having the general form of a skew bevel gear in which theteeth extend from the outer peripherygof the gear to an inner circleremote from the axis, the hob having arcuate gashes struck upon radii ofa length greater than the radius of the offset circle,'the' centers ofthe radii lying upon a circle having a. diameter at least as great asthe diameter of the offset circle.

In witness whereof I have hereunto subscribed my name.

CARL G. OLSON.

